Intrapreneurship is a sense of entrepreneurship within the employees themselves. The fact that intrapreneurship could affect the competitive advantage in any company is true and it is in this research that this statement is proved in a family business called PD Indo Diesel Medan. In this particular family business, intrapreneurship is implemented not only by the successor of the business himself but also by other loyal and motivated employees. In this way, the company has something else that can improve their overall quality which other companies might not have. The objectives of this research are to investigate if PD Indo Diesel Medan’s competitive advantage is indeed affected by the intrapreneurship sense that the employees have and how the family business has managed to nurture this ability. The research methods that are used in this research include the descriptive and correlative methods. From this research, we can conclude that: 1) The competitive advantage of PD Indo Diesel Medan is affected by the intrapreneurship sense that the employees have. 2) PD Indo Diesel Medan constantly nurtures the employees’ sense of intrapreneurship by providing trainings and motivations. 3) There is a strong and positive correlation between intrapreneurship and competitive advantage in PD Indo Diesel Medan. However, only 40.5% of the competitive advantage is affected by the intrapreneurship while the rest 59.5% is affected by other factors.Therefore, it is important for the family business to continue motivating the employees in terms of contributing creative ideas or solutions to the issues that might arise in PD Indo Diesel.